**4. Conclusion**

Enzymes are useful for industrial chemical reactions, and the role of biochemical engineers was to study the industrial use of enzymes. However, most of the enzymes that occur in nature do not have sufficient activity for industrial use, and the bioreactors were not as successful as expected. Directed evolution technology is proposed to overcome these problems. Artificial enzymes have been drastically produced by exploiting the direct evolution technology. The technology may be advanced by using editing tools such as TALEN and CRISPR/Cas9. Artificial microorganisms whose genomes are directly improved using CRISPR/Cas9 may be more suitable than recombinant *E. coli* for use as bioreactors. As such, biochemical engineers will play more important roles in the development of bioreactors in the future.
